In a first debugging technique, a hardware emulator program is provided on the host computer which is performing the debugging. Such emulators however can only provide limited functionality, and are generally undesirable
In a technique used by the Applicants for communicating with embedded digital processors, so-called “on-chip emulators” are used. The function of an on-chip emulator device is to monitor and control the operation of the digital signal processor. Such devices typically have storage capability, and are able to initiate command and control sequences for the digital processor in response to externally applied signals from a host computer or in response to detected states of the digital processor.
Communication between the on-chip emulation device and the host computer is carried out via a link, which is typically a link designed for that purpose. Typically, signals over the link are tailored to the particular on-chip emulation device in the interests of efficient debugging.
This however is an inflexible arrangement, and is typically limited to use during “pure” debugging—i.e. pre-production debugging. It would not be suitable for production use, or where the need arises for communication with an embedded system while it is in service—eg to update data or programs stored on the embedded system.